Add memoisation to fibonacci

Author: Zobeir-Rigi

Sprint-2/improve_with_caches/fibonacci/fibonacci.py

@@ -1,4 +1,10 @@
+cache = {0: 0, 1: 1}
+
+
 def fibonacci(n):
-    if n <= 1:
-        return n
-    return fibonacci(n - 1) + fibonacci(n - 2)
+    if n in cache:
+        return cache[n]
+
+    cache[n] = fibonacci(n - 1) + fibonacci(n - 2)
+
+    return cache[n]